Different types of acoustic devices have been used through the years. One type of device is a microphone. In a microelectromechanical system (MEMS) microphone, a MEMS die includes a diaphragm, back plate and a support structure. The MEMS die is supported by a base and is enclosed by a housing (e.g., a cup or cover with walls). A port may extend through the base (for a bottom port device) or through the top of the housing (for a top port device). In any case, sound energy traverses through the port, moves the diaphragm and creates a changing potential between the diaphragm and the back plate, which creates an electrical signal. Microphones are deployed in various types of devices such as personal computers or cellular phones.
Many MEMS microphones have a barometric relief opening through the diaphragm. However, this opening can allow ingress of foreign material into a particularly sensitive part of the microphone structure. The gap between the diaphragm and back plate may be around 4 μm, so is easily filled with contaminants during manufacture or use of the device. These contaminants adversely affected microphone operation.
The problems of previous approaches have resulted in some user dissatisfaction with these previous approaches.
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